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Sellas Life Sciences (SLS) was in the spotlight on Wednesday, after the biotech firm announced a milestone in its pivotal leukemia trial of galinpepimut-S (GPS).
Sellas said that its Phase 3 Regal trial of GPS recorded its 80th event (number of deaths), triggering the final analysis. It will now proceed with database lock, unblinding of the study data, and statistical analysis of the primary endpoint data.
After the analysis, Sellas will announce preliminary topline primary endpoint results later this quarter, though it did not provide a date. SLS shares tanked 18%, their biggest single-day loss since March 2024. SLS has a short interest of 27.3%, according to Koyfin data.
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SLS was also the top trending ticker on Stocktwits at the time of writing.
The 126-patient study tested GPS, an experimental cancer vaccine, in patients with acute myeloid leukemia (AML), who achieved remission after their disease returned. GPS targets a protein found in cancer cells, helping the immune system recognize and attack them.
The trial compares GPS with investigators’ choice of best available treatment to determine overall survival.
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The update comes after an SEC filing on Tuesday showed that BlackRock held 15.87 million shares of the company, representing a 7.9% stake, as of September 30. It held 12.14 million shares at March-end.
Sellas is also developing SLS009, an experimental CDK9 inhibitor for leukemia with topline results expected in the fourth quarter.
The company tested SLS009 on pancreatic cancer cells from patients whose tumors were resistant to another cancer drug, Daraxonrasib. SLS009 showed activity against these cancer cells, and the effects were even stronger when both drugs were used together.
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Retail sentiment surrounding SLS on Stocktwits turned ‘bullish’ from ‘neutral’ over the past 24 hours, amid ‘high’ message volumes. However, commentary was mixed on the selloff.

One bullish user said the sell-off was completely irrational.
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However, another user said the stock could “easily fall 50%+” in the next couple of days.
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Still, SLS is among the top biotech performers so far this year, gaining more than 130%. In comparison, the State Street SPDR S&P Biotech ETF (XBI) has gained about 35%.
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